Reinforced plastics strips

Abstract

 A method of forming a strip of plastics material for use in a vertically suspended curtain is characterised by the steps of extruding a plastics material (3) through a die (2) to form a tube, simultaneously drawing an inextensible fibre (7) through the die (2), within the tube, passing the tube together with the inextensible fibre (7) through pressing means (12), before the plastics material has set, to form a flat strip incorporating the inextensible fibre.

Description

[0001] This invention is concerned with forming reinforced plastics strips, and is especially cooncerned with reinforced plastics strips for use as curtains.

[0002] In the specification of British Patent 1604436 there is described a method of forming a strip having rounded edges of plastics material, comprising extruding the material as a tube through a circular die, and before the material solidifies, pressing the tube flat so as to form a strip. A plurality of such strips when suspended vertically can form a curtain.

[0003] Curtains of this kind may be used in, for example, industrial premisses to seal off doorways or openings. The use of such curtains helps to reduce the transmission of noise and heat from one side of the doorway to the other.

[0004] The strips for forming curtains described in the above specification are of a plastics material and it has been found in practice that when suspended from a horizontal support rail the strips tend to elongate, so that if they are initially cut to the correct length for the height of a doorway opening they tend after a period of time to come into contact with the floor surface. This effect is particularly disadvantageous, especially when the doorway is used for the passage of trucks and other vehicles.

[0005] It is an object of the present invention to provide plastic strips of the kind described in the aforesaid patent specification, but which do not suffer from the disadvantage of elongation.

[0006] According to the present invention a method of forming a strip of plastics material for use in a vertically suspended curtain is characterised by the steps of extruding a plastics material through a die to form a tube, simultaneously drawing an inextensible fibre through the die within the tube, passing the tube together with the inextensible fibre through pressing means before the plastics material has set, to form a flat strip incorporating the inextensible fibre.

[0007] The inextensible fibre may be of a textile nature, such as, a twisted polypropylene, polyester, polyamide or other fibre, or may be a natural fibre such as cotton flax etc.

[0008] It is desirable that the inextensible fibre be compatible with the plastics material forming the tube so that as the tube is passed through the pressing means to form a flat strip, the material of the fibre is incorporated into the inner walls of the synthetic plastics material of the tube and is firmly embedded therein. It is preferable that the pressing means comprises nip rollers.

[0009] By the use of the inextensible fibre, the strips when suspended vertically will not elongate and hence the disadvantage of the strips described and referred to in the specification of British Patent 1604436 is overcome.

[0010] Reference is now made to the accompanying drawings in which:

Figure 1 shows a schematic diagram of apparatus for use in a method of forming a reinforced plastics strip in accordance with the invention; and

Figure 2 is a section on the lines 2-2 of Figure 1.

[0011] In the drawings a plastics extruder generally designated 1 is provided with an extrusion head 2, through which a plastics material 3 is extruded.

[0012] A cone-shaped floor stand 4 is attached to the plastics extruder 1 by means of a bar 5. The stand 4 supports five reels 6, each of which can provide a supply of polyester fibre 7.

[0013] An air supply may be connected to one leg 9a of a two legged spider 2a. The fibres 7 are delivered to a second leg 9b of the spider 2a.

[0014] A tension screw 8 is provided to allow adjustment of the tension of the fibres 7.

[0015] The plastics extruder 1 is mounted upon a hollow central shaft which extends axially of the extruder. A fibre guiding tube guides the fibres from the second leg of the spider into the central shaft. The fibre guiding tube curves as it enters the central shaft and then extends along the central shaft through the extrusion head 2. The fibre guiding tube should preferably be manufactured from a hardened steel.

[0016] Air may pass through the extrusion head 2 along the central shaft and surrounding the fibre guiding tube. The air is supplied to the central shaft through an air control pipe connected to the first leg 9a of the spider.

[0017] A spacer bar 10 is located in front of the extrusion head 2, but behind a nip roller unit 11 which contains nip rollers 12.

[0018] In use, the plastics material 3 is extruded in the form of an air blown tubular bubble, the supply of air being provided from the air supply through the air control pipe and the central shaft.

[0019] The fibres 7 are drawn from their respective reels into the extruder 1 and are guided through the fibre guide tube until they are inside the tubular bubble. The spacer bar 10 serves the purpose of separating the fibres so that they are evenly distributed, and are substantially parallel to each other within the tubular bubble.

[0020] The tubular bubble together with the fibres then pass to the nip roller unit 11, where the tubular bubble is flattened by the nip rollers 12.

[0021] The plastics material 3 leaves the nip roller unit 11 as a flat strip having rounded edges, and incorporating the fibres 7 (as illustrated in Figure 2).

Claims

1. A method of forming a strip of plastics material for use in a vertically suspended curtain is characterised by the steps of extruding a plastics material through a die to form a tube, simultaneously drawing an inextensible fibre through the die, within the tube, passing the tube together with the inextensible fibre through pressing means, before the plastics material has set, to form a flat strip incorporating the inextensible fibre.

2. A method according to Claim 1 in which the inextensible fibre is formed from a polypropylene, polyester or polyamide fibre.

3. A method according to Claim 1 in which the inextensible fibre is formed from cotton flax.

4. A method according to any preceding claim in which the inextensible fibres are passed through a spacer bar, before being passed through the pressing means, in order to evenly arrange the fibres within the tube in parallel-spaced relationship with each other.

5. A method according to any preceding claim in which the pressing means comprise nip rollers.

Drawing